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  MO17 - Radiotherapy I: Stereotactic Ablative Body Radiotherapy (ID 106)

  • Event: WCLC 2013
  • Type: Mini Oral Abstract Session
  • Track: Radiation Oncology + Radiotherapy
  • Presentations: 1
  • Moderators:M. Zwitter, S.K. Vinod
  • Coordinates: 10/29/2013, 16:15 - 17:45, Bayside 204 A+B, Level 2

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    MO17.11 - Stereotactic ablative radiotherapy (SABR) for centrally located early-stage or isolated parenchymal recurrences of non-small cell lung cancer (NSCLC): How to fly in a "no fly zone" (ID 1961)

    17:15 - 17:20  |  Author(s): P. Balter
    • Abstract
    • Presentation
    • Slides

    Background
    SABR has become a standard treatment option for medically inoperable, peripherally located early-stage NSCLC. However, using SABR for centrally located lesions remains challenging because of the potential for severe side effects. Here we sought to validate our previous experience with SABR (50 Gy in 4 fractions) for central lesions, including the dose-volume constraints, and explore a new regimen of 70 Gy in 10 fractions for cases in which dose-volume constraints cannot be met with the previous regimen.

    Methods
    We used 4D-based, volumetric image-guided SABR to treat 101 patients with biopsy-proven and PET/CT-staged centrally located (within 2 cm of bronchial tree, trachea, major vessels, esophagus, heart, pericardium, brachial plexus or vertebral body) T1-2N0M0 tumors (n=82) or isolated lung-parenchyma recurrent lesions (n=19). The treatment period spanned February 2005 through May 2011; follow-up visits (every 3 months for 2 years and every 6 months for the next 3 years) included chest CT or PET/CT. Endpoints were toxicity (CTCAE v3.0), survival, local control, regional control, and distant metastasis.

    Results
    At a median follow-up time of 30.3 months for all patients (40.5 months for those alive), median overall survival time was 56.5 months and 5-year overall survival rate was 49.0%. Three-year actuarial local, regional, and distant control rates were 96.5%, 87.2% and 77.3%. The most common toxicities were chest-wall pain (18% grade 1 and 13% grade 2) and radiation pneumonitis (10.9% grade 2 and 1.9% grade 3). No patient experienced grade 4 toxicity and one patient with tumor invading bronchial tree who received 70 Gy in 10 fractions died from hemoptysis 13 months after SABR. The distance between tumor and chest was associated with chest wall pain (≤1 cm 45% vs >1 cm 17%, p=0.002). Univariate and multivariate analyses showed that for the 82 patients receiving 50 Gy in 4 fractions, mean total lung dose (MLD) >5 Gy or ipsilateral lung V~20~ (iV~20~) >16% were independent predictors of radiation pneumonitis; 3 of 9 patients in that group with D~max~ to brachial plexus >35 Gy experienced brachial neuropathy versus none of the 73 patients with brachial D~max~ ≤ 35 Gy (p=0.001).

    Conclusion
    SABR for centrally located lesions produces clinical outcomes similar to those for peripheral lesions when normal tissue constraints are respected. For 50 Gy in 4 fractions, we recommend MLD ≤5 Gy, lung iV~20~ ≤16%; bronchial tree D~max~ ≤ 38 Gy, V~35~ ≤1 cm[3]; major vessel D~max~≤ 56 Gy, V~40~≤1 cm[3]; esophageal D~max~ ≤35 Gy, V~30~≤1 cm[3 ]; brachial plexus D~max~ ≤35 Gy, V~30~≤0.2 cm[3] and spinal cord D~max~ <25 Gy. Giving 70 Gy in 10 fractions is another option for challenging cases but can produce severe toxicity if significant amounts of critical structures are exposed to ≥70 Gy. Proper selection of cases (based on tumor location and normal tissue constraints) and SABR regimens and volumetric image-guided delivery are all crucial to avoid overdosing critical structures. Typically, a minimum 5-10 mm distance between critical structures and gross tumor is required to meet dose-volume constraints.

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